Đáp án:
A
Giải thích các bước giải:
Ta có:
$\begin{gathered}
I = \frac{{{U_R}}}{R} = \frac{{30}}{{15}} = 2 \hfill \\
U_d^2 = U_r^2 + U_L^2 \hfill \\
\Rightarrow {40^2} = U_r^2 + U_L^2\left( 1 \right) \hfill \\
{U^2} = U_L^2 + {\left( {{U_r} + {U_R}} \right)^2} \Rightarrow U_L^2 + {\left( {{U_r} + 30} \right)^2} = {60^2}\left( 2 \right) \hfill \\
\left( 1 \right)\left( 2 \right) \Rightarrow {U_r} = \frac{{55}}{3} \hfill \\
P = UI\cos \varphi = U.I.\frac{{{U_R} + {U_r}}}{U} = 60.2.\frac{{30 + \frac{{55}}{3}}}{{60}} = \frac{{290}}{3}\left( {\text{W}} \right) \hfill \\
\end{gathered} $
